Bases are reagents which are widely used for various reactions such as hydrolysis reactions, polymerization reactions, color reactions, redox reactions, neutralization reactions, etc. For example, various recording materials such as silver salt photographic materials and diazotype photographic materials require a base during an image forming process.
An image may be formed on a recording material by a wet developing process using a treating solution (developing solution) or a dry developing process (e.g., heat developing process). A base may be contained in the developing solution, when an image is formed by the wet process such as a developing process. On the other hand, when an image is formed by a dry process, the base is previously incorporated into a recording material. However, the base incorporated into the recording material sometimes causes a problem with respect to the stability of the recording material. For example, the base may adversely affected the other ingredients in the recording material or the base itself may be deteriorated during the storage of the recording material.
In order to eliminate the above-mentioned problem, it has been proposed to use a base precursor in place of the base. The base precursor is a neutral or weakly basic compound and can form a base during the image forming process. In a heat developable recording material, a heat decomposition type base precursor is preferably used. Various kinds of the heat decomposition type base precursors have been studied and proposed. A typical example of the heat decomposition type base precursor is a salt of an organic base with a carboxylic acid. The base precursors in the form of a salt of an organic base with a carboxylic acid are described in U.S. Pat. No. 3,493,374 (triazine compound and carboxylic acid), U.K. Pat. No. 998,949 (trichloroacetate), Japanese Patent Provisional Publication No. 59(1984)-180537 (propiolate), and Japanese Patent Provisional Publication No. 61(1986)-51139 and U.S. Pat. No. 4,060,420 (sulfonylacetate). These base precursors release a base when the carboxyl group in the carboxylic acid undergoes decarboxylation at an elevated temperature.
It has been demanded to find out a base precursor which is stable during storage but is quickly decomposed to form a base when it is heated. In the above-mentioned publications, a prime attention is paid to a decarboxylation of the carboxyl group of the carboxylic acid, and the carboxylic acid is mainly studied.
However, these base precursors do not fully meet both of the two demands for stability during storage and for quick base formation.